You're apparently still on this challenge (according to what I can see here : your own profile). I can also see that you're still active on the website (last validation is not older than a week).

If you seek for some clues for this hack you need to read, and understand, this carefully:

TheRiddla said:

It seems ‘hackers’ successfully hijacked the e-mail submission form...
We have indeed received quite a lot of advertisement e-mails about Viagra, but we can't explain how it would be possible to send e-mails to other addresses...

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This might aim you to the main objective which is to send e-mails to other addresses. Let's say yours ? (-:
So according to the source code you need to seek how/what to hack to do so.